EAPSI: Development of a Stable Transformation System in the Red Alga Porphyra Umbilicalis

Royer Charlotte J, Bangor ME

Investigators

Abstract

Bacteria are critical to the normal development of multicellular organisms, including algae, and bacteria may help algae survive environmental stresses, but these associations remain poorly understood. The red alga Porphyra umbilicalis ('laver') experiences intertidal stresses that include high temperature, high light, and desiccation, but the alga recovers quickly when submerged again at high tide. Laver is currently the subject of an extensive bacterial microbiome study, and now has a fully-sequenced genome, making it an ideal candidate for investigations of how bacterial associations confer stress tolerance on a molecular level. One way to enable these investigations is to create a system to manipulate laver?s genes, i.e. stable genetic transformation. This work is proposed in collaboration with Dr. Hiroyuki Mizuta and Dr. Toshiki Uji of Hokkaido University, Japan. Dr. Uji is a leading expert on genetic transformation in red algae, and he and his colleagues recently developed a stable transformation system for nori (Pyropia yezoensis), a Pacific cousin of laver. A stable transformation system will allow research to be conducted on stress responses in laver, including possible effects of the microbiome, and will provide an invaluable tool for other scientific studies based on the Porphyra genome. The primary goal of this work is to establish the first stable transformation system in P. umbilicalis. Plasmids containing a heat shock factor (HSF) gene and a selectable marker (hygromycin B resistance) will be inserted via particle bombardment into both P. umbilicalis and P. yezoensis. Germination and development of transformed protoplasts or neutral spores will be evaluated, and transformants of both species will be subjected to comparative heat shock treatments and their HSF expression analyzed. This comparison is useful because P. umbilicalis and P. yezoensis are related members of one of the oldest eukaryotic groups (Bangiophyceae), and they are both economically and culturally important algae. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.